Akamai (AKAM-1.8%) shares sink after Citigroup lowers its rating to Sell from Neutral, citing valuation after an "overly aggressive" stock price reaction to last month's purchase of Cotendo and greater competition from Amazon's (AMZN) CloudFront CDN business. On the Cotendo deal, it is “not clear that Cotendo will provide Akamai material new products of market opportunities."